Heat control for automatic choke



Dec. 20, 1960 H. A. CARLSON HEAT CONTROL FOR AUTOMATIC CHOKE Filed Aug. 12, 1957 INVENTOR. HAROLD A. CARLSON BY A? ATTORNEY v United States Patent 2,965,082 HEAT CONTROL FOR AUTOMATIC CHOKE Harold A. Carlson, Brentwood, Mo., assignor to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Aug. 12, 1957, Ser. No. 677,537 V a 7 Claims. (Cl. 123-119) 2,965,082 Patented Dec. 20, 1960 "ice prising an air horn section 3, a main body section 4, and a throttle section 6. An air inlet passage 7 in the air horn section communicates with a mixture conduit 8, which extends through the main body section and throttle section to deliver a fuel-air mixture to the intake manifold of an internal combustion engine.

A choke valve 9, provided in the air inlet passage, is fixed on a shaft 11 journaled at its ends in the air horn section 3. The main body section 4 is provided with a venturi stack and a main fuel nozzle 12 for discharging liquid fuel into a primary venturi 13. The main .body section is adapted to be provided with a conventional constant level fuel bowl (not shown) to supply fuel through a main fuel passage and an idle fuel passage to the main fuel nozzle 12 and idle fuel port 14, respectively. A

throttle valve 16 is fixed on a shaft 17 journaled in the the richness of the fuel-air mixture supplied to the engine.

In the operation of such devices, the temperature responsive means acts to bias the choke valve toward its closed position, when the engine is cold, to provide a relative rich mixture for starting. As the engine warms up, the

throttle section 6, and is adapted to be connected to an accelerator pedal by any suitable conventional linkage.

The choke valve 9 is actuated by an automatic'choke control mechanism, which is shown as comprising a housing 18 having a partition 19 and a cover 21 secured thereto by suitable fastening means, such as screws 22 and clips 23. A crank 24 is fixed on one end of the choke shaft 11, within the housing, for engagement by the outer end 25 of a coiled bimetal thermostat 26 disposed between v the partition 19 and cover 21. The inner end of the temperature responsive means permits the suction re sponsive means to gradually move the choke valve to full open position to provide a relatively lean, economical mixture.

After stopping of a heated engine, the temperature responsive means cools off more rapidly than the engine and acts to move the choke valve to closedposition while the engine'is still in a warm or heated condition, thereby providing a rich fuel mixture during restarting of the heated engine. As it is not necessary or desirable to supply a rich fuel mixture during restarting of a heated engine, it is an object of the present invention to provide an automatic choke control mechanism which maintains the choke valve in an open position when the engine is in a heated condition to thereby provide a relatively lean fuel mixture.

Another object of the invention is to provide an automatic choke control mechanism, embodying temperature and suction responsive means to actuate a choke valve, in which heat is transmitted through a metallic rod or cable from the engine to the temperature responsive means for the purpose of maintaining the choke valve in open position when the engine is in a heated condition.

A further object of the invention resides in the provision of an automatic choke control mechanism in which the metallic heat conducting rod is connected to the inner end of a spirally wound bimetal thermostat provided to actuate the choke valve.

Another object of the invention is to provide an automatic choke control mechanism, in which the metallic heat conducting rod is enclosed within the usual hot air conduit leading from an exhaust manifold of an engine to the interior of a housing containing the thermostat.

The invention embodies other novel features, details of construction, and arrangement of parts which are hereinafter set forth in the specification and claims, and illustrated in the accompanying drawings, wherein:

Fig. 1 is a fragmentary vertical sectional view illus' trating an automatic choke control mechanism embodying features of the invention.

Fig. 2 is a fragmentary sectional view illustrating a modified form of the invention.

Referring now to the drawings for a better understanding of the invention and, more particularly, to Fig. 1 therein, the automatic choke control mechanism is shown as applied to a conventional downdraft carburetor comto a stove 29 provided in the exhaust manifold 31 of an thermostat 26 is secured to' a plug 27 fixed on the cover 21, the plug being formed of metal having a high coefficient of heat conductivity.

A hot air conduit 28 is connected at one end thereof engine, and is connected at its other end to the plug 27 by means of a nut 32. The plug 27 is formed with apertures 33 leading from the conduit 28 to the interior of the housing 18. A rod or cable 34, formed of metal having a relatively high coeflicient of heat conductivity, is soldered, welded, or otherwise secured to the outer end of the metal plug 27 at 30, and extends through the conduit 28 to the interior of the stove 29. If desired, a cover 35 of suitable heat insulating material may be provided on the conduit 28.

The automatic choke controlmechanism is provided with a suction responsive means comprising a piston 36 mounted in a cylinder 37 and connected to the crank 24 by a link 38. The wall of the cylinder 37 is formed with a by-pass groove 39 for the passage of air from atmosphere'to a suction chamber 41 provided with a suction passage 42 leading to a port 43 in the mixture conduit 8 posterior to the throttle valve 16.

In the operation of the automatic choke control mechanism thus shown and described for starting a cold engine, the choke valve 9 is urged to closed position by the thermostat 26, when the engine starts firing, to provide a rich fuel mixture. As the engine warms up, heated air is delivered from the stove 29 through the conduit 28 to the interior of the housing 18 for the purpose of heating the bimetal thermostat to cause the free end 25 thereof to gradually move away from the end of the crank 24. During heating of the thermostat, intake manifold suction causes the piston 36 to bias the choke valve 9 toward its full open position to thereby lean out the fuel mixture supplied to the engine. After the engine is stopped, the thermostat gradually cools off and acts through the crank 24 to move the choke valve 9 toward its closed position.

Hcretofore, in the operation of conventional choke control mechanisms for carburetors, the thermostat would cool off more rapidly than the engine and thereby close the choke valve to supply a rich fuel mixture during restarting of a heated engine. In order to delay the choke closing action of the thermostat until the engine has become sufliciently cooled oif to require a rich fuel mixture, the rod or cable 34 is heated in the stove 29 during opera- 3 tion of the engine and conducts some of the heat to the metal plug 29 and thermostat 26.

As the heat conductor rod 34 will retain heat for a period of time substantially equal to the. time required to cool the engine, and as suchheat is conducted fromthe rod. through the plug 27 to the thermostat, closing of the choke valve 9 by the thermostat is delayeduntil the engine is sufiiciently cool to require a rich fuel mixture for, starting. In restarting a heated engine, the, choke valve will remain in open position to provide a relatively lean fuel mixt re- Fig. 2 illustrates a modified form of automatic choke control, mechanism, in Which the heat conducting rod, 34 is inserted into a water jacket or oil pan 41 to be heated by the fluid contained therein during operation of the engine. Upon stopping of the engine, the rod 34 serves as a source of heat for the thermostat 26 to delay closing of the choke valve until the engine temperature has been reduced to a predetermined range. A hot air conduit 42 leads from the stove 29 to an inlet 44 in the housing 18. This form of the invention is otherwise similar in construction and operation to the form heretofore shown and described. 1

Certain structures have been described herein which will fulfill all the objects of the present invention, but it is contemplated that other modifications will be obvious to those skilled in the art which come within the scope of the invention as defined by the appended claims.

I claim:

1. In a carburetor choke, control mechanism for an internal combustion engine, a choke valve, temperature responsive means to actuate said choke valve, and heat conducting means connecting said temperature responsive means with a remote source of engine heat to delay operation of said temperature responsive means when the engine is in a heated condition to provide a relatively lean fuel mixture for restarting the heated engine.

2. In a carburetor choke control mechanism for an internal combustion engine, a choke valve, temperature responsive means to actuate said choke valve, and heat transfer means including heat conducting means and convecting means connecting said temperature responsive means with a remote source of engine heat.

3. In a carburetor choke control mechanism for an internal combust on engine, a choke valve, temperature responsive. means to, actuate said choke valve, and: heat conducting means connecting said temperature responsive means with afremotesource of engine heat, said temperature responsive meanscomprisi-ng a coiled bimetallic strip connected to said heat conducting means.

4. In a carburetor choke controlrnechanism for an internal combustion engine a choke valve, temperature responsive means to actuate said choke valve, and heat conducting means connecting said temperature responsive means with a remote source of engine heat, said temperature responsive means comprising a coiled bimetal strip connected. to said heat conducting. means and acting to close said choke valve responsive to adecrease in temperature.

5. A mechanism according to. claim 1: wherein, said heat conducting means comprising, a metal, rod connected to an exhaust manifold stove.v

6. A mechanism according to claim. 3 wherein, said heat, conducting means is heated by a liquid provided in the engine. I

7. A mechanism according to claim, 1 wherein, said heat conducting means comprises a. metal rod extending through a hot. air conduit provided to direct heated air from said source of engine heat. into. a housing containing, said temperature responsive means.

References Cited in the file of this patent UNITED STATES PATENTS 

